This paper presents a hybrid push/pull streaming scheme to take advantage of both the interval caching-based push method and the mesh-based pull method. When a new peer joins, a mesh-based pull method is adopted to avoid the overhead to reorganize the structure only if all of its potential preceding peers are likely to leave before the end of its playback. Otherwise, an interval caching-based push method is adopted so that the better performance of the push method can be maintained until it completes the playback. We demonstrate that our proposed scheme outperforms compared with when either the interval caching-based push method or mesh-based pull method is employed alone.

With the fast development of mobile communication technologies, mobile multimedia services like mobile Video on Demand (VOD) are becoming prevalent. However, VOD streaming requires dedicated bandwidth to satisfy Quality of Service (QoS), and the limited wireless bandwidth will become insufficient to support the increasing number of mobile VOD users. In order to solve the problem, this paper proposes a Call Admission Control (CAC) approach which can accept new users even when the system bandwidth is insufficient. Our approach also guarantees continuous playback for subscribers by taking into account the service end time and the delay bound of the users. Simulation results demonstrate that the proposed scheme can increase the number of concurrent users and reduce the connection blocking probability significantly without playback interruption.

In Video on Demand (VoD) services, the demand for content items greatly changes daily over the course of the day. Because service providers are required to maintain a stable service during peak hours, they need to design system resources on the basis of peak demand time, so reducing the server load at peak times is important. To reduce the peak load of a content server, we propose to multicast popular content items to all users independently of actual requests as well as providing on-demand unicast delivery. With this solution, however, the hit ratio of pre-distributed content items is small, and large-capacity storage is required at each set-top box (STB). We can expect to cope with this problem by limiting the number of pre-distributed content items or clustering users based on their viewing histories. We evaluated the effect of these techniques by using actual VoD access log data. We also evaluated the total cost of the multicast pre-distribution VoD system with the proposed two techniques.

In Video-on-Demand (VoD) services, the playback continuity is one of the most crucial factors for end-user to judge service quality. It is even more significant than the actual video image quality since new generation VoD users commonly have heterogeneous requirements on service according to their context. Moreover, managing dynamic situations in VoD service is always a challenge, especially in the unpredictable user preferences and network conditions. In this paper, i) Autonomous Decentralized VoD System (ADVODS) has been proposed to satisfy different service quality demands of users and, ii) the Autonomous Node Allocation Technology (ANAT) is proposed for assuring service continuity. With the help of autonomous nodes and mobile agents, ANAT can applies different backup policies to users with different Service Level Agreements (SLA), and dynamically update the backup schema to adapt the changing situations such as various service time or congestion events. Drawing on the evaluation results this paper shows that proposed system architecture has a better performance on streaming service provision and continuity.

The patching technique has been used for reducing initial waiting time in VOD services. Traditionally the technique has been applied to fixed segment NVOD scheduling. However, variable segment NVOD scheduling is known to have a better server bandwidth and less initial waiting time. In this paper, we propose a new scheduling algorithm for a true VOD service by incorporating the patching technique into variable segment NVOD scheduling. Our algorithm provides jitter-free playback while minimizing the use of the patching bandwidth. We present the proof of the correctness of our algorithm.

User Generated Content (UGC) VoD services such as YouTube are becoming more and more popular, and their maintenance costs are growing as well. Many P2P solutions have been proposed to reduce server load in such systems, but almost all of them focus on the single-video approach, which only has limited effect on the systems serving short videos such as UGC. The purpose of this paper is to investigate the potential of an alternative approach, the multi-video approach, and we use a very simple method called collaborative caching to show that methods using the multi-video approach are generally more suitable for current UGC VoD systems. We also study the influence of the major design factors through simulations and provide guidelines for efficiently building systems with this method.

Vertical handoff is required to achieve anywhere and anytime internet access in the fourth generation (4G) network providing interoperability between universal mobile telecommunications system (UMTS) and wireless LAN (WLAN). However, video data can be lost due to latency caused by vertical handoff. To solve this problem, in this paper, we propose a video streaming technique supporting error concealment (EC) for video on demand (VOD) services that provides seamless playout at the client in vertical handoff. In the proposed method, the streaming server first predicts the client buffer status (CBS). Using the predicted CBS and the channel rate, the streaming server selects a proper video transmission method for vertical handoff between frame selective pre (FSP)-transmission and re-transmission. Performance evaluations are presented to demonstrate the effectiveness of the proposed method.

At present, a demand to the technology of contents distribution by which each user can request the desired content through network is increasing. There are some merits and demerits respectively with the existing on-demand systems for contents distribution, such as the methods based on broadcast and select transfer or multicast one. In this paper, we propose a hybrid scheduling method which adaptively uses both broadcasting and multicasting in order to improve the system efficiency. Adequate channel boundary to adopt two different transfer mechanisms is found through analytical consideration. Also, performance improvement of our proposal is verified in terms of response time and request blocking rate through computer simulation.

Providing efficient Video-On-Demand (VOD) service on Broadband Cable Networks (BCNs) is still a challenging issue, although BCNs have been the most important form of broadband services in the US. To address this issue, we have proposed the optimal full-sharing scheduling approach that minimizes the bandwidth consumption of video sessions [1]. We have shown that full-sharing scheduling has remarkable advantages in minimizing the bandwidth consumption of VOD service on BCNs. Furthermore, we design two adaptation algorithms in this paper, which not only keep bandwidth consumption minimal but also significantly reduce the mean service delay.

In this paper, we propose multicast technique in order to reduce the required network bandwidth by n times, by merging the adjacent multicasts depending on the number of HENs (Head-End-Nodes) n that request the same video. Allowing new clients to immediately join an existing multicast through patching improves the efficiency of the multicast and offers services without any initial latency. A client might have to download data through two channels simultaneously, one for multicast and the other for patching. Each video stream is divided into blocks which are the same size of multicast grouping interval Im. Blocks then are evenly distributed into different HENs according to their popularity and the order of requests. Only when the playback time exceeds the amount of cached video data, server generates new multicast channel. Since the interval of multicast can be dynamically expanded according to the popularity of videos, it can be reduced the server's workload and the network bandwidth. We adopt the cache replacement strategy as LFU (Least-Frequently-Used) for popular videos, LRU (Least-Recently-Used) for unpopular videos, and the method for replacing the first block of video last to reduce end-to-end latency. We perform simulations to compare its performance with that of conventional multicast. From simulation results, we confirm that the proposed multicast technique offers substantially better performance.

This paper discusses several practical issues related to the provision of video-on-demand (VOD) services, focusing on retrieval of video data from disk on the server. First, with regard to system design, the pros and cons of cycle-based scheduling algorithms for VOD servers are compared, and an adequate policy according to system configuration is presented. Second, we present a way to tune the cycle-based scheduling algorithm so that it maximizes profit. Third, a method to overcome the cons of cycle-based scheduling algorithms is proposed, and its cost is analyzed.

File system buffers provide memory space for data being transferred to and from disk and act as caches for the recently used blocks, and the buffer manager usually reads ahead data blocks to minimize the number of disk accesses. However, if several multimedia files with different consumption rates are accessed simultaneously from the file system in which LRU buffer replacement strategy is used, the read-ahead blocks of the low rate file are unloaded from memory to be used for loading a data block of a high data rate file, therefore they should be reloaded again into memory from disk when these blocks are actually referenced. This paper proposes and implements a new buffer cache management scheme for a multimedia file system and analyzes the performance of the proposed scheme by modifying the file system kernel of FreeBSD. In this proposed scheme, initially, some buffers are allocated to each opened multimedia file, privately, then these buffers are reused for other data blocks of that file when they are loaded from the disk. Moreover, the number of private buffers allocated for the file is dynamically adjusted according to its data rate. An admission control scheme is also proposed to prevent opening of a new file which may cause overloads in the file system. Experimental results comparing proposed scheme with the original FreeBSD and a simple CTL-based model show that the proposed buffer management scheme could support the realtime play back of several multimedia files with various data rates concurrently without helps of a realtime CPU and disk scheduling.

This paper investigates the lossless video aggregation and transport, a concept of transmitting a group of video sessions as a bundle over a communication network. We focus on the design of optimal transmission plan with minimum receiver buffer requirement for stored variable bit-rate (VBR) videos over a constant bit-rate (CBR) channel without incurring buffer underflow and overflow. For a single video, an efficient algorithm is proposed to calculate the optimal transmission plan in only O(N) time, a significant improvement of the previous result with time complexity of O(N2log N). For multiple video sessions, we propose an aggregation scheme to calculate the changes of optimal transmission plans at the joints or separations, where a session bundled in the aggregated video stream begins or stops. The experimental results show that our algorithms stand out in terms of simplicity and efficiency.

Video-on-Demand (VOD)servers are becoming feasible. These servers are a building component in a heterogeneous multimedia environment but have voluminous data to store and manage. If only disk-based secondary storage systems are used to store and manage this huge amount of data the system cost would be extensively high. A tape-based tertiary storage system seems to be a reasonable solution to lowering the cost of storage and management of this continuous data. However, the usage of a tertiary storage system to store large continuous data introduces several issues. These are mainly the replacement policy on disks, the decomposition and the placement of continuous data chunks on tapes, and the scheduling of multiple requests for materializing objects from tapes to disks. In this paper we address these issues and we propose solutions based on some heuristics we experimented in a simulator.

In this paper, we point out an architecture optimization problem for networks delivering services such as Video-On-Demand or, more precisely, two intertwined problems, i.e., the storage allocation of the videos among the storage nodes of the network and the choice of the network topology. We present and investigate the properties of a genetic algorithm which can handle such problems. This algorithm, as well as a greedy heuristics and simulated annealing, are then used to derive solutions in function of link and node cost parameters in a 36-node network. The results show that genetic algorithms are an effective class of algorithms for such problems, and possibly many other topology optimization problems.

Internet is evolving to be an integrated service platform for promising future global information infrastructure. New multimedia services, e.g., Video-on-Demand, are expected to be provided on this platform, in conjuction with the existing rich information exchange and sharing services on Internet, such as E-mail, WWW. The paper proposes a service system architecture for Video-on -Demand on Internet, named MINS (Multimedia Internet Navigation System), which is capable of both realtime audio/video transmission and realtime and VCR like plya-out. MINS is composed of 1) servers maintaining both audio/video program lists and contents, and 2) clients retrieving the programs and play-out them. The paper focuses on the communication architecture in MINS, e.g., flow control, realtime media synchronization control, and audio/video session control. The performance of the prototype MINS is also evaluated in the paper.

This paper presents the system issues involved with the transmission of pre-encoded VBR MPEG video using CBR service. Conventional wisdom suggests that lossless delivery of VBR video using CBR service requires bandwidth to be reserved at the peak rate resulting in low bandwidth utilization. We calculate the minimum rate at which bandwidth must be reserved on a network in order to provide continuous playback of an MPEG encoded video bitstream. Simulation results using the frame size traces from several pre-encoded MPEG bitstreams and several buffer sizes demonstrate that this minimum reservation rateis much lower than the peak rate when a relatively small playback buffer size is used, resulting in much higher bandwidth utilization. Procedures for performing connection setup and lossless realtime video playback between the video server and the client are outlined. Methods for incorporating VCR-like features such as pauseandfast forward/reversefor Video-on-Demand (VoD) applications are presented.

Many activities are being promoted for the coming multimedia age. In this paper, background information for multimedia communications is followed by an outline of joint tests in multimedia communications with some examples of the projects and applications. These trials are also explained from the aspects of project specifications, which include application classifications and details of multimedia-on-demand offerings, as well as technical issues in experimental environments which mainly include those related to ATM technology.

In this paper, the real-time scheduling mechanism which could support multimedia retrieval services more efficiently is investigated. In order to support multimedia service, the MEDF (modified earliest deadline first) algorithm that takes advantage of the priority queue and the virtual deadline mechanism is proposed. Additionally, its performance is analyzed and compared with conventional RR (round robin), FCFS (first come first serve), SS (sporadic server), MRF (minimum remained-time first), and EDF (earliest deadline first) algorithms. According to the simulation results, the proposed MEDF algorithm shows better performance than other scheduling algorithms in the multimedia environments.